Aerial and aerial system



July 24, 19.314 E. GREEN 1,967,881

AERIAL AND AERIAL SYSTEM Filed sept. 7, 1929 Egg@ Ely. 2 ,Fg 5

INVENTOR N ERNEST GREEN ATTORN EY Patented July 24, 1934 AERIAL ANDAERIAL SYSTEM Ernest Green, London, England, assigner t RadioCorporation of America, a corporation of Delaware Application September7, 1929, Serial No. 390,963 In Great Britain September i9, 1928 l Claim.

This invention relates to aerials and aerial systems, and moreparticularly to aerial arrangements for use in .directive wirelesssignalling.

-In the specifications of British Patents Nos.

242,342 and 285,106 are described aerials adapted to be excited from oneend, which are long in comparison with the wave length employed, and inwhich radiation is suppressed either wholly or in part from alternatehalf wave lengths of the aerials. The non-radiating portions or" such anaerial (which portions may be termed phasing elements) were formed invarious ways; for example, by folding the aerial wire back upon itselfso as to produce substantial cancellation of radiation, or byconstituting the length of the aerial from which radiation was to besuppressed by inductance and/or capacity. The present invention has forits principal object to provide improved phasing elements for directiveaerials.

According to this invention the phasing element or elements of adirective aerial or .aerial system is or are constituted by atransmission line or lines, i. e. a line or lines in which inductanceand capacity are substantially uniformly distributed over the lengththereof.

in one form of construction, an aerial comprises a plurality ofradiating sections alternating with a plurality of phasing elementsconstituted each by a solenoid having a diameter small in comparisonwith its length. Alternatively a single solenoid separating a pair ofradiating sections may be replaced by a plurality of solenoids inparallel.

The effect of the phasing elements depends upon their lengths, theirpositions in the aerial and the ratios of their surge impedances to thatof the aerial itself; normally, however, the phasing elements should bearranged to suppress radiation from alternate half wave lengths. They 40may be each greater than, equal to, or less than a half wave inelectrical length.

If the radiating sections and the phasing elements are each a half wavelength in electrical length, the phase of the current in the radiating45 sections will be substantially the same for all values of the surgeimpedance of the phasing element. Such an aerial will give maximumradiation at right angles to its length.

If the radiating sections are longer than a half wave length and thephasing elements shorter, the relative phasing of the current in theradiating sections will depend upon the ratios of the surge impedancesof the phasing elements to that of the aerial. If the surge impedance of-the phasing elements is equal to that of the aerial,

(Cl. Z50-33) f y the currents in the radiating sections will be in phaseand the aerial will give its maximum radiation in directions at rightangles to itself, whilst if the said surge impedance differs from thatofy the aerial, the currents in the radiating sections will differ inphase and the direction of maximum radiation will be deflected towardsor away from the free end of the aerial, according as the surgeimpedance of the phasing elements is less or greater thanthat of theaerial.

If the radiating sections are shorter than a half wave length, andthe'phasing elements longer, the direction of maximum radiation will beat right angles to the line of the aerial, or deiected I i towards oraway from the free end of the aerial, m according as the surge impedanceof the phasing elements is equal to, greater than or less than the surgeimpedance of the aerial.

There is also the case in which the terminal load of a radiating sectionis made to be that of a pure resistance. This may be effected either bylocating the said load at a nodal point or by adding a suitable value ofinductance and/or capacity. If to this point of the aerial there isconnected a phasing element whose surge impedance is equal to theterminal resistance of the aerial, and if an E. M. F. be applied to theother end of the said phasing element, the phase of the current in theaerial will be controlled by the U length of the phasing element.

For example, suppose a half wave aerial giving a pure resistance load atits lower end to be connected at that end through a phasing elementwhose surge impedance is equal to the said resistance load to a lowerand similar aerial. Then, if the length of the phasing element is a halfwave, the phase of the current in the two aerials will be the same.

It will be seen that the phase of the current in the upper aerial may bemade to lag or lead that in the lower to any desired extent byincreasing or decreasing the electrical length of the said phasingelement. The direction of maximum radiation can therefore be controlledby varying the length of the said phasing element.

Phasing elements of the type described provide a ready means ofcontrolling the phase of the currents in the radiating sections, andtherefore the direction of maximum radiation of aerials that are long incomparison with the Wave length. Such elements may be employed in asimilar manner with single aerials or in aerial systems comprising acombination o-f aerials forming, for example, a so-called beam aerialsystem.

If desired, the phasing elements may be formed as transmission linesconstituted by a section of aerial wire bent back upon itself one ormore times so as to be substantially nonradiating. For example, Wherethe aerial consists of several wires in parallel, a phasing element mayconsist of a single Wire doubled back upon itself. The employment ofsuch folded back aerial sections to secure suppressed or reducedradiation from alternate half wave lengths of an aerial is not per separt of the present invention, and it forms part of the subject matterof the British Patents Nos. 242,342 and 285,106 already referred to.

The invention is illustrated in the accompanying drawing, in whichvarious embodiments in accordance therewith are shown diagrammatically.

Referring to Figure 1, this shows an aerial energized from the bottom asindicated, and comprising three radiating sections AB, CD, EF, each ahalf wave long and which alternate with phasing elements BC, DE. Thephasing elements are constituted by solenoids whose diameter is smallcompared with the length. The current distribution in the aerial isrepresented by the dotted curved line.

Figure 2 shows a slight modification, differing from that of Figure 1only in that radiating sections AB, CD, EF exceed a half wave in length.

In the arrangement shown in Figure 3, the phasing elements areconstituted each by a plurality of similar relatively small diametersolenoids in parallel. It will be appreciated that this arrangementrenders it a comparatively simple matter for the phasing elements to bedesigned to have any desired value of surge impedance.

Figure 4 shows an arrangement structurally resembling those of Figures 1and 2, but in which the phasing element BC is designed to have a surgeimpedance equivalent to a pure resistance R1 equal to the load of theradiating section AB measured at B, the surge impedence of the phasingelement DE being equivalent to a pure resistance R2 equal to thecombined load of the two radiating sections AB, CD measured at D. Therelative phases of the currents in the radiating sections AB, CD, EF aredetermined by the electrical lengths of the phasing elements BC, DE.

In the modification shown in Figure 5, the radiating sections GH, MNconsist each of a plurality of wires in parallel (as shown three wiresin parallel), and the phasingrelement consists of a single wire HIJKLMbent back and forth lupon itself and supported by means of insulators S.

Having now particularly described and ascertained the nature of my saidinvention and in what manner the same is to be performed, I declare thatwhat I claim isz- A directive antenna comprising a plurality of equallength coaxial radiating sections which are electrically shorter thano-ne half wave length, and a plurality of phasing elements which arelonger electrically than one half wave length connecting said radiatingsections together.

ERNEST GREEN.

